Such a method is used in bus systems, also referred to as data bus systems, such as fieldbus systems, which are to be Internet Protocol-enabled to guarantee direct data traffic into the Internet, corporate network or similar higher-order data networks, etc, with the bus systems operating on an input/output level, like for example PROFINET or similar systems, which can be used for automation systems. This allows automation components, sensors, actuators or similar technical components for example to be controlled or data to be exchanged directly from the higher-order data network (Internet, etc.).
The term automation system here and in the document as a whole refers to a system which uses technical means to carry out specific operations partially or wholly according to predetermined programs without human intervention. Operations in this context refer for example to manufacturing processes, assembly processes, transport processes, quality control processes, etc., which operate in particular in the industrial environment.
Conversely Internet technologies are also available in the bus system. This technology thus joins the Internet and the bus system together to form a network in a virtual manner for the user, the transparency of the bus system being increased in a sustainable manner in the process.
The most important protocol for network coupling at present is the Internet Protocol, the principal task of which is to provide cross-network addressing. However it does not improve services in the underlying networks or layers to any significant degree. The Internet protocol operates in a connectionless manner by exchanging data telegrams, also referred to as datagrams or frames. Datagrams thereby comprise data packets, provided with an IP header, which contains information relating to length, sender and recipient addresses and protocol designator.
Sender and recipient addresses are specified in 32-bit fields and comprise details of the network and the line located therein. In such cases a datagram comprises an IP header and an IP data field. The IP header contains for example the address of the end recipient. If said end recipient is in a different network from the sender, direct transmission is not possible. Instead a router (also referred to as a gateway in the Internet) in the sender's own network is addressed and this forwards the information based on what are known as routing tables. The encapsulation principle can be used here, with the datagram of the other network being encapsulated in the IP data field, to be “extracted” at the gateway for forwarding in the other network.
A network coupler is known from WO 2004/071025 A1, which is connected on the one hand to a network, on which Ethernet telegrams can be transmitted, and on the other hand to a number of subscribers, who are connected to the network coupler via an internal interface. To exchange data, an Ethernet telegram received via the external interface of the network coupler is forwarded to the internal Ethernet interface of the network coupler and output on the ring transmission path, with each subscriber connected to the interface exchanging the useful data intended for the respective subscriber using the Ethernet telegram circulating on the ring transmission path.